After production began, the M14 rifle experienced occasional failures where the bolt did not strip the next round from the magazine and so closed on an empty chamber. Sometimes, the bolt would contact the cartridge halfway through the cycle causing a jam. This occurred because the bolt speed increased with using ball-shaped gunpowder while the M14 rifle had been originally designed to use ammunition loaded with extruded gunpowder.

Springfield Armory redesigned the magazine spring to help raise the rear end of the follower and shortened the rear end of the cylindrical portion of the operating rod by 0.1 ”. The shortening of the operating rod increased the bolt cycle time to give the magazine spring sufficient time to raise the top cartridge to where it needed to be. These changes were successful in eliminating the cartridge stripping problem.

In the early 1960s, U. S. Marines used the M14 rifles with fixed bayonets for Close Quarters Battle training. When Marines executed the movement known as the vertical slash, the stock would sometimes disengage from the front band causing the barrel to separate from the stock. Also, a similar problem occurred when the Marines used the M14 rifle as a step to hurdle over obstacles. Two Marines would hold the rifle, one at either end while a third Marine stepped on to the rifle in the middle to clear a fence or wall. To keep the stock from separating from the barrel under such combat conditions, the gas cylinder was redesigned to incorporate a lip just aft of the bottom gas port to support the front band (see Miscellaneous Notes on USGI Parts).

The most common failures of the M14 rifles while in service were cracked stocks and rear sight pinions, missing rear sight nuts, and misaligned flash suppressors. Less common failures were broken safeties, broken firing pins, and out of specification gas cylinders. The least common problems were broken extractors and bolt locks. No problems were reported with the operating rod, trigger group (except safety), butt plate, or front sight. There were two versions of the M14 extractor.

The early version was identical to the M1 Garand rifle extractor and had a sharp point on the lower front right-hand corner which could snag the cartridge. This caused the extractor to leave the bolt when firing M82 blank cartridges. This problem was corrected with the late version (January, 1965 and onward) extractor which was milled with a beveled lower front corner which allowed the M82 cartridge to clear the extractor. Repeated automatic fire from the hip with the M14E2 stock will cause it to crack at or near the pistol grip joint.

No projectile weighing over 168 grains should be used in an unmodified M14 type rifle with standard barrel chamber. 3 This is because of increased chamber and gas port pressure with heavier bullets. Thunderbird Cartridge Company (Laveen, AZ) tested some M118 ammunition for Smith Enterprise in 1990. The chamber pressure measured from 53,000 to over 59,000 cupric units of pressure (CUP). The adjusted average chamber pressure was 57,000 cupric units of pressure at 78 degrees Fahrenheit. U. S. Army M14 rifles in Iraq in 2004 were experiencing overpressure problems with M118LR 175 grain ammunition. An M14 rifle may safely shoot M118LR ammunition if the barrel chamber is reamed to the M118LR chamber dimensions. At the time of this writing, Smith Enterprise, Inc. is the only firm with a M118LR cartridge chamber reamer. The M118LR reamer is made only for Smith Enterprise, Inc. by Dave Manson Precision Reamers (Grand Blanc, MI). Dave Manson started Dave Manson Precision Reamers in 1999 after having worked at Clymer Manufacturing Company for sixteen years as Production Manager.

Ammunition must NEVER be loaded by hand into the chamber with the bolt allowed to close at full speed driven the operating rod spring. That practice presents the risk of slam fire. Ammunition should instead be fed only from the magazine. Always point all firearms in a safe direction and always assume a loaded chamber for safety reasons.

The user should not attempt to engage the safety on an M14 type rifle unless the hammer is cocked. Otherwise, the safety can fail. Other components of the trigger group are remarkably trouble-free and durable, so long as amateurish “trigger jobs” are avoided.

Based on civilian experience, USGI gas pistons have a useful life between 10,000 and 15,000 rounds. USGI gas cylinders will require replacement after approximately 40,000 rounds. Flash suppressor prongs experience signs of gas erosion near the muzzle after thousands of rounds fired. The prongs will eventually crack at some point after 15,000 rounds.
Some Viet Nam War veterans have stated that the M14 magazine feed lips could and did bend when hitting the deck hard in a combat situation. While this is a true statement, it is not unique to the M14 rifle. This is a concern with most other magazine fed military rifles as well.

Some M14 type rifles have left the factory with loose flash suppressors and operating rod guides. The flash suppressor nut can be over-tightened causing slight stretching of the barrel. This was an issue with XM21 and M21 rifles. The gas cylinder plug can and has loosened during firing and in combat at that. The prepared M14 type rifle owner always carries a M14 combination tool to check the gas cylinder plug on a routine basis. Once these parts are correctly installed, the M14 rifle is almost always trouble free. If the bolt does not cycle after the first shot is fired check the spindle valve to see if it is in the open position (slot in the vertical). The wise M14 rifle owner carries a spare complete bolt assembly already headspaced to the rifle.

A few M1A receivers under serial number 020000 tend to wear prematurely on the elevation serrations. These receivers can be heat treated and the surface hardness increased to correct this condition. The design of the standard windage knob detents prevents similar problems on that side of the receivers.

There have been cases where commercial manufacture extractors have flown out of the bolt while the rifle is cycling. These extractors can usually be made serviceable by further machining of the divot where the extractor spring plunger rests on the extractor, or by replacing the extractor spring plunger. An alternate solution is to replace the commercially-made extractor with a USGI extractor. Often, the commercial extractor spring tension is incorrect, the extractor spring detent is too large or the extractor stem is too long.

Chinese M14 type gas cylinders and gas cylinder plugs are prone to rusting because they are not made of stainless steel. Chromium plating on the Chinese gas pistons makes rust less of a problem with that part.

From late 2001 when M14 rifles were fielded with the 82nd Airborne Division until the present day operations in Afghanistan and Iraq, the U. S. Army suffers from a dearth of armorer expertise to maintain the M14 rifle in combat theaters at the Direct Support and General Support maintenance levels. Nonetheless, the M14 rifle has proven itself over and over in combat with even less-than-adequate support.

ripsaw

Excellent post, now a relatively new problem is rearing its ugly head from SAI rifles, some of the bolt stops are catching the edge of the bolt and causing failure to feed from left side. It is quick fix if handled properly though. I know several that have sent them back to SAI and they return with usgi bolt stop installed, problem solved. Others have simply filed off some of the stop, not that I would recommend this because i do not know how deep the hardening is for this piece.

Rapidrob

I had 40 M-14 in my armory while serving in Viet Nam. The only problem I remember putting in my logs were the gas plug shooting loose causing a FTE and Breakfree CLP getting into the gas cylinder causing the rifle not cycle.(system must be dry)
I'm glad to see the the rifle is used in the Sand Box as it is an accurate rifle. I still shoot my Navy issue M1A Match rifle and have worn out one barrel and am working on the second. The only problem I have ever had was as you posted, the ejector leaving the bolt due to a too shallow retaining slot.

Rainman74

No projectile weighing over 168 grains should be used in an unmodified M14 type rifle with standard barrel chamber. 3 This is because of increased chamber and gas port pressure with heavier bullets.

Does this include the M1A or just the M14?

Different

Either M14 or M1A unless the rifle (either M14 or M1A) has been modified for heavier projectiles.